Image processing device and method for operating image processing device

ABSTRACT

An image processing device includes a multimedia intellectual property (IP) block which processes image data including a first component and a second component; a memory; and a frame buffer compressor (FBC) which compresses the image data to generate compressed data and stores the compressed data in the memory. The frame buffer compressor includes a logic circuit which controls a compression sequence of the first component and the second component of the image data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. 119 toKorean Patent Application No. 10-2018-0010128, filed on Jan. 26, 2018,and Korean Patent Application No. 10-2018-0041786, filed on Apr. 10,2018, in the Korean Intellectual Property Office, the disclosures ofwhich are incorporated by reference in their entireties herein.

BACKGROUND 1. Technical Field

The present disclosure relates to an image processing device and amethod for operating an image processing device.

2. Discussion of Related Art

More and more applications demand high-definition video images andhigh-frame rate images. Accordingly, the amount of data accessed from amemory (i.e., the bandwidth) storing these images by various multimediaIntellectual Property (IP) blocks of image processing devices hasgreatly increased.

Each image processing device has limited processing capability. When thebandwidth increases, the processing capability of the image processingdevice may reach this limit. Accordingly, a user of the image processingdevice may experience a decrease in speed while recording or playing avideo image.

SUMMARY

An aspect of the present disclosure provides an image processing devicethat executes compression of image data having excellent compressionquality.

Another aspect of the present disclosure provides a method for operatingan image processing device that executes compression of image datahaving excellent compression quality.

According to an aspect of the present disclosure, there is provided animage processing device including a multimedia intellectual property(IP) block configured to process image data including a first componentand a second component; a memory; and a frame buffer compressor (FBC)configured to compress the image data to generate compressed data andstore the compressed data in the memory, wherein the frame buffercompressor includes a logic circuit configured to control a compressionsequence of the first component and the second component of the imagedata.

According to another aspect of the present disclosure, there is providedan image processing device including a multimedia intellectual property(IP) block configured to process image data conforming to a YUV format;a memory; and a frame buffer compressor (FBC) configured to compress theimage data to generate compressed data and store the compressed data inthe memory, wherein the frame buffer compressor includes a logic circuitconfigured to control a compression sequence such that compression of achroma component including Cb and Cr components of the YUV format of theimage data is executed prior to compression of a luma componentincluding Y component of the YUV format of the image data.

According to another aspect of the present disclosure, there is provideda method for operating an image processing device including calculatinga total target bit based on a target compression ratio of image dataconforming to a YUV format; calculating a chroma component target bitfor compressing a chroma component including Cb and Cr components of theYUV format; assigning the chroma component target bit to compress thechroma component; calculating the luma component target bit of the lumacomponent including a Y component of the YUV format, using the chromacomponent used bit of the compressed data for the chroma component;assigning the luma component target bit to compress the luma component;and adding a dummy bit after the compressed data of the luma component,when the sum of the luma component used bit of the compressed data ofthe luma component and the chroma component used bit is less than thetotal target bit.

The aspects the present disclosure are not limited to those mentionedabove and another aspect which is not mentioned is clearly understood bya person skilled in the art from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent by describing in detailexemplary embodiments thereof with reference to the attached drawings,in which:

FIGS. 1 to 3 are block diagrams for explaining an image processingdevice according to some embodiments of the present inventive concept;

FIG. 4 is a block diagram for explaining the frame buffer compressor ofFIGS. 1 to 3 in detail;

FIG. 5 is a block diagram for explaining an encoder of FIG. 4 in detail;

FIG. 6 is a block diagram for explaining a decoder of FIG. 4 in detail;

FIG. 7 is a conceptual diagram for explaining three operation modes ofYUV 420 format data of the image processing device according to anexemplary embodiment of the present inventive concept;

FIG. 8 is a conceptual diagram for explaining three operation modes ofYUV 422 format data of the image processing device according to anexemplary embodiment of the present inventive concept;

FIGS. 9 to 11 are schematic views for explaining the operation of animage processing device for YUV 420 format data according to anexemplary embodiment of the present inventive concept;

FIGS. 12 to 14 are schematic views for explaining the operation of animage processing device for YUV 422 format data according to anexemplary embodiment of the present inventive concept; and

FIG. 15 is a flowchart illustrating a method for operating the imageprocessing device according to an exemplary embodiment of the presentinventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1 to 3 are block diagrams for explaining an image processingdevice according to an exemplary embodiment of the present inventiveconcept.

Referring to FIG. 1, the image processing device according to exemplaryembodiments of the present inventive concept includes a multimedia IP(Intellectual Property) 100 (e.g., an IP block, and IP core, a circuitetc.), a frame buffer compressor (FBC) 200 (e.g., a circuit, a digitalsignal processor, etc.), a memory 30, and a system bus 400.

In an embodiment, the multimedia IP 100 is a part of the imageprocessing device that directly executes the image processing of theimage processing device. The multimedia IP 100 may include a pluralityof modules for recording and reproducing images such as camcoding andplayback of video images.

The multimedia IP 100 receives the first data (e.g., image data) from anoutside source such as a camera, and converts the first data into seconddata. For example, the first data may be moving image data or image rawdata. The second data is data generated by the multimedia IP 100, andmay include data resulting from the multimedia IP 100 processing thefirst data. The multimedia IP 100 may repeatedly store the second datain the memory 300 and update the second data via various steps. Thesecond data may include all the data used in these steps. The seconddata may be stored in the memory 300 in the form of third data.Therefore, the second data may be data before stored in the memory 300or after read from the memory 300. This will be explained in more detailbelow.

In an exemplary embodiment, the multimedia IP 100 includes an imagesignal processor ISP 110, a shake correction module G2D 120, amulti-format codec MFC 130, a GPU 140 and a display 150. However, thepresent inventive concept is not limited thereto. That is, themultimedia IP 100 may include at least one of the image signal processor110, the shake correction module 120, the multi-format codec 130, theGPU 140 and the display 150. The multimedia IP 100 may be implemented bya processing module (e.g., processor) that accesses the memory 300 inorder to process data representing moving or static images.

The image signal processor 110 receives the first data, andpre-processes the first data to convert the first data into the seconddata. In an exemplary embodiment, the first data is an RGB type imagesource data. For example, the image signal processor 110 may convert thefirst data of the RGB type into a second data of the YUV type.

In an embodiment, the RGB type data means a data format which expressescolors on the basis of the three primary colors of light. That is, it isa type that expresses images, using three kinds of colors of red (RED),green (GREEN), and blue (BLUE). In contrast, the YUV type means a dataformat which separately expresses brightness, that is, a luma signal anda chroma signal. That is, Y means the luma signal, and U(Cb) and V(Cr)mean chroma signals, respectively. U means a difference between the lumasignal and the blue signal component, and V means a difference betweenthe luma signal and the red signal component.

The YUV type data may be acquired by converting the RGB type data usinga conversion formula. For example, a conversion formula such asY=0.3R+0.59G+0.11B, U=(B−Y)×0.493, V=(R−Y)×0.877 may be used to convertthe RGB type data into the YUV type data.

Since human eyes are sensitive to the luma signal but are less sensitiveto the color signal, the YUV type data may be more easily compressedthan RGB type data. As a result, the image signal processor 110 mayconvert the first data of the RGB type into the second data of the YUVtype.

The image signal processor 110 converts the first data into the seconddata and then stores the second data in the memory 300.

The shake correction module 120 may perform the shake correction ofstatic image data or moving image data. The shake correction module 120may perform the shake correction by reading the first data or the seconddata stored in the memory 300. In an embodiment, the shake correctionmeans the detection of shaking of the camera from the moving image dataand removal of the shaking from the moving image data.

The shake correction module 120 may correct the shaking of the firstdata or the second data to update the first data or the second data andstore the updated data in the memory 300.

The multi-format codec 130 may be a codec that compresses the movingimage data. In general, since the size of the moving image data is verylarge, a compression module that reduces its size is necessary. Themoving image data may be compressed via association among a plurality offrames, and this compression may be performed by the multi-format codec130. The multi-format codec 130 may read and compress the first data orthe second data stored in the memory 300.

The multi-format codec 130 may compress the first data or the seconddata to generate new second data or updates the second data to store itin the memory 300.

The GPU (Graphics Processing Unit) 140 may perform arithmetic processand generation of two-dimensional or three-dimensional graphics. The GPU140 may arithmetically process the first data or the second data storedin the memory 300. The GPU 140 may be specialized for graphic dataprocessing to process the graphic data in parallel.

The GPU 140 may compress the first data or the second data to generateupdated first data or updated second data and store the updated data inthe memory 300.

The display 150 may display the second data stored in the memory 300 ona screen. The display 150 may display image data processed by componentsof the multimedia IP 100, that is, the image signal processor 110, theshake correction module 120, the multi-format codec 130 and the GPU 140.However, the present inventive concept is not limited to these examples.

The image signal processor 110, the shake correction module 120, themulti-format codec 130, the GPU 140 and the display 150 of themultimedia IP 100 may individually operate, respectively. That is, theimage signal processor 110, the shake correction module 120, themulti-format codec 130, the GPU 140 and the display 150 may individuallyaccess the memory 300 to write or read data.

In an embodiment, the frame buffer compressor 200 compresses the seconddata to convert the second data into the third data before themultimedia IP 100 individually accesses the memory 300. The frame buffercompressor 200 transmits the third data to the multimedia IP 100, andthe multimedia IP 100 transmits the third data to the memory 300.

As a result, the third data compressed by the frame buffer compressor200 is stored in the memory 300. Conversely, the third data stored inthe memory 300 may be loaded by the multimedia IP 100 and transmitted tothe frame buffer compressor 200. In an embodiment, the frame buffercompressor 200 decompresses the third data to convert the third datainto the second data. The frame buffer compressor 200 may transmit thesecond data (i.e., the decompressed data) to the multimedia IP 100.

In an embodiment, each time the image signal processor 110, the shakecorrection module 120, the multi-format codec 130, the GPU 140 and thedisplay 150 of the multimedia IP 100 individually access the memory 300,the frame buffer compressor 200 compresses the second data to the thirddata and transfer it to the memory 300. For example, after one of thecomponents of the multimedia IP 100 generates and stores the second datain the memory 300, the frame buffer compressor 200 can compress thestored data and store the compressed data into the memory 300. In anembodiment, each time a data request is transmitted from the memory 300to the image signal processor 110, the shake correction module 120, themulti-format codec 130, the GPU 140 and the display 150 of themultimedia IP, the frame buffer compressor 200 decompresses the thirddata into the second data, and transmits the second data to the imagedata processor 110, the shake correction module 120, the multi-formatcodec 130, the GPU 140 and the display 150 of the multimedia IP 100,respectively.

The memory 300 stores the third data generated by the frame buffercompressor 200, and may provide the stored third data to the framebuffer compressor 200 so that the frame buffer compressor 200 candecompress the third data.

In an embodiment, the multimedia IP 100 and the memory 300 are connectedto the system bus 400. Specifically, the image signal processor 110, theshake correction module 120, the multi-format codec 130, the GPU 140 andthe display 150 of the multimedia IP 100 may be individually connectedto the system bus 400. The system bus 400 may be a path through whichthe image signal processor 110, the shake correction module 120, themulti-format codec 130, the GPU 140, the display 150 and the memory 300of the multimedia IP 100 transfer data to each other.

The frame buffer compressor 200 is not connected to the system bus 400,and perform the operation of converting the second data into the thirddata and converting the third data into the second data, when the imagesignal processor 110, the shake correction module 120, the multi-formatcodec 130, the GPU 140 and the display 150 of the multimedia IP 100access the memory, respectively.

Next, referring to FIG. 2, the frame buffer compressor 200 of the imageprocessing device according to an exemplary embodiment of the presentinventive concept is directly connected to the system bus 400.

The frame buffer compressor 200 is not directly connected to themultimedia IP 100 and is connected to the multimedia IP 100 via thesystem bus 400. Specifically, each of the image signal processor 110,the shake correction module 120, the multi-format codec 130, the GPU 140and the display 150 of the multimedia IP 100 may transmit the data toand from the frame buffer compressor 200 through the system bus 400, andmay transmit the data to the memory 300 accordingly.

That is, in the process of compression, each of the image signalprocessor 110, the shake correction module 120, the multi-format codec130, the GPU 140 and the display 150 of the multimedia IP 100 maytransmit the second data to the frame buffer compressor 200 through thesystem bus 400. Subsequently, the frame buffer compressor 200 maycompress the second data into the third data and transmit the third datato the memory 300 via the system bus 400.

Likewise, even in the process of decompression, the frame buffercompressor 200 may receive the third data stored in the memory 300 viathe system bus 400, and may decompress it to the second data.Subsequently, the frame buffer compressor 200 may transmit the seconddata to each of the image signal processor 110, the shake correctionmodule 120, the multi-format codec 130, the GPU 140 and the display 150of the multimedia IP 100 via the system bus 400.

Referring to FIG. 3, in an image processing device according to anexemplary embodiment of the present inventive concept, a memory 300 anda system bus 400 are connected to each other via a frame buffercompressor 200.

That is, the memory 300 is not directly connected to the system bus 400but is connected to the system bus 400 only via the frame buffercompressor 200. Further, the image signal processor 110, the shakecorrection module 120, the multi-format codec 130, the GPU 140 and thedisplay 150 of the multimedia IP 100 are directly connected to thesystem bus 400. Therefore, the image signal processor 110, the shakecorrection module 120, the multi-format codec 130, the GPU 140 and thedisplay 150 of the multimedia IP 100 access the memory 300 only throughthe frame buffer compressor 200.

In the present specification, the second data is referred to as an imagedata 10, and the third data is referred to as compressed data 20.

FIG. 4 is a block diagram for explaining the frame buffer compressor ofFIGS. 1 to 3 in detail.

Referring to FIG. 4, the frame buffer compressor 200 includes an encoder210 (e.g., an encoding circuit) and a decoder 220 (e.g., a decodingcircuit).

The encoder 210 may receive the image data 10 from the multimedia IP 100to generate the compressed data 20. The image data 10 may be transmittedfrom each of the image signal processor 110, the shake correction module120, the multi-format codec 130, the GPU 140 and the display 150 of themultimedia IP 100. The compressed data 20 may be transmitted to thememory 300 via the multimedia IP 100 and the system bus 400.

Conversely, the decoder 220 may decompress the compressed data 20 storedin the memory 300 into the image data 10. The image data 10 may betransferred to the multimedia IP 100. The image data 10 may betransmitted to each of the image signal processor 110, the shakecorrection module 120, the multi-format codec 130, the GPU 140 and thedisplay 150 of the multimedia IP 100.

FIG. 5 is a block diagram for explaining the encoder of FIG. 4 indetail.

Referring to FIG. 5, the encoder 210 includes a first mode selector 219(e.g., a logic circuit), a prediction module 211 (e.g., a logiccircuit), a quantization module 213 (e.g., a logic circuit), an entropyencoding module 215 (e.g., a logic circuit) and a padding module 217(e.g., a logic circuit).

In an embodiment, the first mode selector 219 determines whether theencoder 210 operates in a lossless mode or a lossy mode. When theencoder 210 operates in the lossless mode in accordance with the firstmode selector 219, the image data 10 is compressed along the losslesspath (Lossless) of FIG. 5, and when the encoder 210 operates in thelossy mode, the image data 10 is compressed along the lossy path(Lossy).

The first mode selector 219 may receive a signal from the multimedia IP100 which is used to determine whether to perform the losslesscompression or perform the lossy compression. The lossless compressionmeans compression without loss of data. A compression ratio may changedepending on the data being losslessly compressed. Unlike losslesscompression, the lossy compression is compression in which data ispartly lost. The lossy compression has a higher compression ratio thanthe lossless compression, and may have a fixed compression ratio set inadvance.

In the case of the lossless mode, the first mode selector 219 enablesthe image data 10 to flow along the lossless path (Lossless) to theprediction module 211, the entropy encoding module 215 and the paddingmodule 217. Conversely, in the lossy mode, the first mode selector 219enables the image data 10 to flow along the lossy path (Lossy) to theprediction module 211, the quantization module 213 and the entropyencoding module 215.

The prediction module 211 may compress the image data 10 by dividing theimage data 10 into prediction data and residual data. The predictiondata and the residual data together take up less space than the imagedata 10. In an embodiment, the prediction data is image data of onepixel of the image data and the residual data is created from thedifferences between the prediction data and the image data of the pixelsof the image data that are adjacent the one pixel. For example, if theimage data of the one pixel has a value between 0 and 255, 8 bits may beneeded to represent this value. When the adjacent pixels have similarvalues to that of the one pixel, the residual data of each of theadjacent pixels is much smaller than prediction data, and thus thenumber of data bits of representing the image data may be greatlyreduced. For example, when pixels having values of 253, 254, and 255 areconsecutive, if the prediction data is set as 253, the residual datarepresentation of (253 (prediction), 1 (residue), and 2 (residue)) issufficient, and the number of bits per pixel for expressing theseresidual data may greatly decreased from 8 bits to 2 bits. For example,24 bits of data of 253, 254, and 255 can be reduced to 12 bits due to 8bit prediction data of 253 (11111101), 2 bit residual data of 254−251=1(01), and 2 bit residual data of 255−253=2 (10).

Therefore, the prediction module 211 may compress the overall size ofthe image data 10 by dividing the image data 10 into the prediction dataand the residual data. Various methods are available for setting thetype of the prediction data.

The prediction module 211 may perform prediction on a pixel basis or mayperform prediction on a block basis. In this case, the block may mean aregion formed by a plurality of adjacent pixels. For example, predictionon a pixel basis could mean that all the residual data is created fromone of the pixels, and prediction on the block basis could mean thatresidual data is created for each block from a pixel of thecorresponding block.

The quantization module 213 may further compress the image data 10 thatwas compressed by the prediction module 211. In an exemplary embodiment,the quantization module 213 removes the lower bits of the image data 10through the preset quantization coefficient. Specifically, therepresentative value is selected by multiplying the data by thequantization coefficient, but a loss may occur by truncating the decimalpart. If the value of the pixel data is between 0 and 2-1 (=255), thequantization coefficient may be defined as/(2^(n)−1)12(n−1) (where, n isan integer equal to or less than 8). However, the present embodiment isnot limited thereto. For example, if the prediction data is 253(11111101), the prediction data can be reduced from 8 bits to 6 bits byremoving the lower 2 bits, which results in prediction data of (111111)252.

However, the removed lower bits are not restored later and thus arelost. Therefore, the quantization module 213 is utilized only in thelossy mode. However, since the lossy mode has compression ratiorelatively higher than that in the lossless mode and may have a fixedcompression ratio set in advance, information on the compression ratiois not separately required later.

The entropy encoding module 215 may compress the image data 10compressed by the quantization module 213 in the lossy mode or the imagedata 10 compressed by the prediction module 211 in the lossless modethrough entropy coding. In an embodiment, the entropy coding utilizes amethod for assigning a number of bits depending on the frequency.

In an exemplary embodiment, the entropy encoding module 215 compressesthe image data 10, using Huffman coding. In an alternative embodiment,the entropy encoding module 215 compresses the image data 10 viaexponential golomb coding or golomb rice coding. In an exemplaryembodiment, the entropy encoding module 215 determines an entropy codingvalue (e.g., a k value) from the data it is to be compress, creates atable from the value of k and compresses the image data 10 using thetable.

The padding module 217 may perform padding on the image data 10compressed by the entropy encoding module 215 in the lossless mode.Here, the padding may mean addition of meaningless data to match aspecific size. This will be explained in more detail below.

The padding module 217 may be enabled not only in the lossless mode butalso in the lossy mode. In the lossy mode, the image data 10 may becompressed further than the desired compression ratio when compressed bythe quantization module 213. In such a case, even in the lossy mode, theimage data 10 may be converted into the compressed data 20 via thepadding module 217 and transmitted to the memory 300. In an exemplaryembodiment, the padding module 217 is omitted so that no padding isperformed.

The compression management module 218 controls the compression sequenceof the first component and the second component of the image data 10.Here, the image data 10 may be image data conforming to the YUV format.

In this case, the first mode selector 219 determines that the encoder210 operates in the lossy mode, and the image data 10 is compressedalong the lossy path (Lossy) of FIG. 5 accordingly. That is, theconfiguration in which the compression management module 218 controlsthe compression sequence of the first component and the second componentof the image data 10 is premised on the case where the frame buffercompressor 200 compresses the image data 10 using a lossy compressionalgorithm.

Specifically, the image data 10 may include a first component and asecond component. Here, the first component may include, for example, aLuma component (corresponding to the aforementioned “luminance signal”)including the Y component of the YUV format, and the second componentmay include, for example, a Chroma component (corresponding to theaforementioned “color difference signal”) including Cb and Cr componentsof the YUV format.

The compression management module 218 determines the compressionsequence of the first component and the second component of the imagedata 10, and the frame buffer compressor 200 decompresses the firstcomponent and the second component in accordance with the compressionsequence determined by the compression management module 218.

That is, if the compression management module 218 determines thecompression sequence of the first component and the second component ofthe image data 10, the frame buffer compressor 200 compresses the imagedata 10 in accordance with the compression sequence, using of theprediction module 211, the quantization module 213 and the entropyencoding module 215 of the encoder 210.

Thereafter, the frame buffer compressor 200 merges the compressed dataof the first component and the compressed data of the second componentto generate a single bit stream, and may write the generated single bitstream to the memory 300. Also, the frame buffer compressor 200 may reada single bit stream from the memory 300, and may decompress the readsingle bit stream to provide the decompressed data to the multimedia IP100.

More details of the compression management module 218 for executing suchan operation will be described later with reference to FIGS. 9 to 15.

FIG. 6 is a block diagram for explaining the decoder of FIG. 4 indetail.

Referring to FIG. 6, the decoder 220 includes a second mode selector 229(e.g., a logic circuit), an unpadding module 227 (e.g., a logiccircuit), an entropy decoding module 225 (e.g., a logic circuit), aninverse quantization module 223 (e.g., a logic circuit), and aprediction compensation module 221 (e.g., a logic circuit).

The second mode selector 229 determines whether or not the compresseddata 20 stored in the memory 300 has been compressed in a losslessmanner or a lossy manner. In an exemplary embodiment, the second modeselector 229 determines whether the compressed data 20 has beencompressed by the lossless mode or the lossy mode through the presenceor absence of the header. This will be explained in more detail below.

In the case of the lossless mode, the second mode selector 229 enablesthe compressed data 20 flow along the lossless path (Lossless) to theunpadding module 227, the entropy decoding module 225 and the predictioncompensation module 221. Conversely, in the case of the lossy mode, thesecond mode selector 229 enables to flow along the lossy path (Lossy) tothe compressed data 20 to the entropy decoding module 225, the inversequantization module 223 and the prediction compensation module 221.

The unpadding module 227 removes the padded portion of the data which ispadded by the padding module 217 of the encoder 210. The unpaddingmodule 227 may be omitted when the padding module 217 is omitted.

The entropy decoding module 225 may decompress the data compressed bythe entropy encoding module 215. The entropy decoding module 225 mayperform the decompression via Huffman coding, exponential golomb codingor golomb rice coding. Since the compressed data 20 includes the kvalue, the entropy decoding module 225 may perform the decoding, usingthe k value.

The inverse quantization module 223 may decompress the data compressedby the quantization module 213. The inverse quantization module 223 mayrestore the compressed data 20 compressed using the quantizationcoefficient determined by the quantization module 213, but it is notpossible to completely restore the part which is lost in the process ofcompression Therefore, the inverse quantization module 223 is utilizedonly in the lossy mode.

The prediction compensation module 221 may restore the data representedby the prediction data and the residual data generated by the predictionmodule 211. The prediction compensation module 221 may, for example,convert the residual data representation of (253 (prediction), 1(residue), and 2 (residue)) into 253, 254, and 255. For example, theprediction compensation module 221 may restore the data by adding theresidual data to the prediction data.

The prediction compensation module 221 may restore the predictionexecuted in units of pixels or blocks in accordance with the predictionmodule 211. As a result, the compressed data 20 may be restored ordecompressed and may be transmitted to the multimedia IP 100.

The decompression management module 228 may perform a work in which thecombination sequence of the first component and the second componentdetermined by the compression management module 218 described abovereferring FIG. 5 to execute the compression of the image data 10 can beproperly reflected when decompressing the compressed data 20.

The image data 10 of the image processing device according to anexemplary embodiment of the present inventive concept is YUV type data.For example, the YUV type data may have a YUV 420 format or a YUV 422format.

FIG. 7 is a conceptual diagram for explaining three operation modes ofYUV 420 format data of the image processing device according to anexemplary embodiment of the present inventive concept.

Referring to FIGS. 1 to 7, the encoder 210 and the decoder 220 of theframe buffer compressor 200 may have three operation modes. The imagedata 10 of the YUV 420 format may have a luminance signal block Y of16×16 size, and a first color difference signal block Cb or U and asecond color difference signal block Cr or V of each of 8×8 sizes. Here,the size of each block means whether to include pixels arranged inseveral rows and columns, and the size of 16×16 means the size of theblock constituted by the plurality of pixels with 16 rows and 16columns.

The frame buffer compressor 200 may include three operation modes of (1)a concatenation mode, (2) a partial concatenation mode, and (3) aseparation mode. These three modes relate to compression formats of thedata and may be operation modes determined separately from the lossymode and the lossless mode.

First, the concatenation mode (1) is an operation mode of compressingand decompressing all the luminance signal blocks Y, the first colordifference signal block Cb and the second color difference signal blockCr. That is, as illustrated in FIG. 5, in the concatenation mode (1),the unit block of compression is a block in which the luminance signalblock Y, the first color difference signal block Cb and the second colordifference signal block Cr are combined. Therefore, the size of the unitblock of compression may be 16×24. For example, in the concatenationmode, all of the blocks (e.g., the Y block, the Cb block, and the Crblock) are combined into a single larger block, and a single compressionoperation is performed on the single larger block.

In the partial concatenation mode (2), the luminance signal block Y isseparately compressed and decompressed, but the first color differencesignal block Cb and the second color difference signal block Cr arecombined with each other and may be compressed and decompressedtogether. As a result, the luminance signal block Y is 16×16 in itsoriginal size, and the block in which the first color difference signalblock Cb and the second color difference signal block Cr are combined isbe 16×8. For example, in the partial concatenation mode, the b block andthe 8×8 Cb block are combined into a second block, a first compressionoperation is performed on the Y block and a second compression operationis separately performed on the second block.

The separation mode (3) is an operation mode of separately compressingand decompressing all the luminance signal block Y, the first colordifference signal block Cb and the second color difference signal blockCr. For example, in the separation mode, a first compression operationis performed on the Y block, a second compression operation is performedon the Cb block, and a third compression operation is performed on theCr block. In an exemplary embodiment, in order to make the sizes of theunit blocks of compression and decompression the same, the luminancesignal block Y is held at the original size of 16×16, but the firstcolor difference signal block Cb and the second color difference signalblock Cr are increased to the size of 16×16. For example, amagnification operation may be performed on the Cb block and Cr block tomake them the same size as the Y block.

As a result, if the number of blocks Y of the luminance signal is N, thenumber of the first color difference signal block Cb and the number ofthe second color difference signal block Cr may be reduced to N/4,respectively.

When the frame buffer compressor 200 of the image processing deviceaccording to an exemplary embodiment of the present inventive concept isoperating in the concatenation mode (1), all the required data may beread through a single access request to the memory 300. In particular,when the RGB type data rather than the YUV type data is required in themultimedia IP 100, the frame buffer compressor 200 may be operate moreefficiently in the concatenation mode (1). This is because it ispossible to acquire the luminance signal block Y, the first colordifference signal block Cb and the second color difference signal blockCr at a same time in the concatenation mode (1), and in order to acquirethe RGB data, all the luminance signal block Y, the first colordifference signal block Cb and the second color difference signal blockCr are required.

The separation mode (3) may require lower hardware resources when thecompression unit block becomes smaller than in the concatenation mode(1). Therefore, when the YUV type data rather than the RGB type isrequired in the multimedia IP 100, the frame buffer compressor 200 maybe operate more efficiently in the separation mode (3).

Finally, the partial concatenation mode (2) is a mode in which there isa compromise between the concatenation mode (1) and the separation mode(3). The partial concatenation mode (2) requires lower hardwareresources than the concatenation mode (1), even when the RGB data isrequired. In the partial concatenation mode (2), the access request tothe memory 300 can be made with a smaller number of times (twice) thanin the separation mode (3).

The first mode selector 219 may choose to compress the image data 10 inany mode among the three modes, that is, the concatenation mode (1), thepartial concatenation modes (2) or the separation mode (3). The firstmode selector 219 may receive a signal from the multimedia IP 100indicating the frame buffer compressor 200 is to operate in a given oneof the available modes of the concatenation mode (1), the partialconcatenation mode (2) and the separation mode (3).

The second mode selector 229 may decompress the compressed data 20depending on the compressed mode of the first mode selector 219, amongthe concatenation mode (1), the partial concatenation mode (2), and theseparation mode (3). For example, if the frame buffer compressor 200 wasrecently used to compress data in the partial concatenation mode (2),the second mode selector 229 could assume data it is to decompress wascompressed using the partial concatenation mode (2).

FIG. 8 is a conceptual diagram for explaining three operation modes ofYUV 422 format data of the image processing device according to anexemplary embodiment of the present inventive concept.

Referring to FIGS. 1 to 6 and 8, the encoder 210 and the decoder 220 ofthe frame buffer compressor 200 also have three operation modes in theYUV 422 format. The image data 10 of the YUV 422 format may have aluminance signal block Y of 16×16 size, and the first color differencesignal blocks (Cb or U) and the second color difference signal blocks(Cr or V) of each of 16×8 size.

In the concatenation mode (1), the unit block of compression is a blockin which the luminance signal block Y, the first color difference signalblock Cb and the second color difference signal block Cr are combinedinto a single larger block. As a result, the size of the unit block ofcompression may be 16×32.

In the partial concatenation mode (2), the luminance signal block Y isseparately compressed and decompressed, but the first color differencesignal block Cb and the second color difference signal block Cr arecombined with each other and compressed and decompressed together. As aresult, the luminance signal block Y is held at its original size of16×16, and the block in which the first color difference signal block Cband the second color difference signal block Cr are coupled may be16×16. Therefore, the size of the block in which the luminance signalblock Y, the first color difference signal block Cb and the second colordifference signal block Cr are combined may be the same.

The separation mode (3) is an operation mode for separately compressingand decompressing all the luminance signal block Y, the first colordifference signal block Cb and the second color difference signal blockCr. In an embodiment, in order to make the size of the unit block ofcompression and decompression the same, the luminance signal block Y isheld at the original size of 16×16, but the first color differencesignal block Cb and the second color difference signal block Cr areincreased to the size of 16×16.

As a result, when the number of luminance signal blocks Y is N, thenumber of the first color difference signal blocks Cb and the number ofthe second color difference signal blocks Cr may be reduced to N/2,respectively.

The operation of the above-described image processing device will now bedescribed with reference to FIGS. 9 to 15. The operation of the imageprocessing device described below may be executed in the concatenationmode (1) described above with reference to FIGS. 7 and 8.

FIGS. 9 to 11 are schematic views for explaining the operation of theimage processing device for the YUV 420 format data according to anexemplary embodiment of the present inventive concept.

FIGS. 9 and 10 illustrate a case where, when the image data 10 conformsto the YUV 420 format, the target compression ratio of the image data 10is 50% and the color depth is 8 bits.

Referring to FIG. 9, the first component of the image data 10, that is,the luma component corresponds to the Y plane 510Y of the image data 10,and the second component of the image data 10, that is, the chromacomponents correspond to the Cb plane 510Cb and the Cr plane 510Cr ofthe image data 10.

In the case of the Y plane 510Y, since the target compression ratio is50% and the color depth is 8 bits, the luma component target bit may becalculated as follows.The luma component target bit=16×16×8×0.5 bit=128×8 bits

In the case of the Cb plane 510Cb and the Cr plane 510Cr, the Cb planecomponent target bit and the Cr plane component target bit may becalculated as follows.Cb plane component target bit=8×8×8×0.5 bit=32×8 bitsCr plane component target bit=8×8×8×0.5 bit=32×8 bits

As a result, the chroma component target bit obtained by combining theCb plane component target bit and the Cr plane component target bit is64×8 bits.

When the luma component and the chroma component are compressed on thebasis of the target bit calculated in this manner, both the lumacomponent and the chroma component are compressed at the samecompression ratio of 50%.

The compressed bit stream 512 corresponding to the compression resultmay be formed as a single bit stream having, for example, the sequenceof a Y component bit stream 512Y, a Cb component bit stream 512Cb, and aCr component bit stream 512Cr. However, the scope of the presentinventive concept is not limited thereto, and the frame buffercompressor 200 may generate a compressed bit stream 512, by merging thecompressed data of the first component and the compressed data of thesecond component in an arbitrary sequence different from the compressionsequence of the first component (e.g., luma component) and the secondcomponent (e.g., chroma component). That is, the sequence of the Ycomponent bit stream 512Y, the Cb component bit stream 512Cb and the Crcomponent bit stream 512Cr in the compressed bit stream 512 may bedifferent from that illustrated in FIG. 9.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 interleaves and merges the compressed data of thefirst component and the compressed data of the second component togenerate a compressed bit stream 512. That is, the Y component bitstream 512Y, the Cb component bit stream 512Cb, and the Cr component bitstream 512Cr may be generated in the compressed bit stream 512, forexample, in the form in which the bit streams of Y, Cb, and Crcomponents repeated in units of pixels of the image data 10 are mixed inan arbitrary sequence.

For example, the compressed bit stream 512 may be interleaved and mergedin the sequence in which a Y component bit stream of the first pixel ofthe image data 10, a Cb component bit stream of the first pixel, a Crcomponent bit stream of the first pixel, a Y component bit stream of thesecond pixel of the image data, a Cb component bit stream of the secondpixel, and a Cr component bit stream of the second pixel are connected,and the interleaving sequence of the Y, Cb, and Cr components may alsobe determined in an arbitrary sequence.

In general, human eyes are more sensitive to changes in brightness thancolor. Therefore, in the image data 10 according to the YUV format, theimportance of the luma component may be higher than the chromacomponent.

However, when compressing the image data 10 according to the YUV format,since the pixel correlation of the chroma component is higher than theluma component, prediction is made easier, and thus, the compressionefficiency of the chroma component becomes higher than the lumacomponent.

Therefore, in order to further improve the compression quality of thecompressed data 20 obtained by compressing the image data 10, a methodof comparatively improving the compression ratio can be applied byassigning more bits than the chroma component with good compressionefficiency to the luma component with lower compression efficiency.

Referring to FIG. 10, the first component of the image data 10, that is,the luma component corresponds to the Y plane 520Y of the image data 10,and the second component of the image data, i.e., the chroma componentcorresponds to the Cb plane 520Cb and the Cr plane 520Cr of the imagedata 10.

In this embodiment, the compression management module 218 controls thecompression sequence so that the frame buffer compressor 200 compressesthe chroma component first and then compresses the luma component. Tothis end, the compression management module 218 calculates the chromacomponent target bit before calculating the luma component target bit.

In the case of the Cb plane 520Cb and the Cr plane 520Cr, each of the Cbplane component target bit and the Cr plane component target bit may becalculated as follows.Cr plane component target bit=8×8×8×0.5 bit=32×8 bitsCr plane component target bit=8×8×8×0.5 bit=32×8 bits

The compression management module 218 allocates the chroma componenttarget bit to first perform compression on the chroma component, beforecalculating the luma component target bit. Specifically, the compressionmanagement module 218 determines a quantization parameter (QP) value andthe entropy k value so that the chroma component used bit is a valuesmaller than and closest to the chroma target bit, thereby performingthe compression on the chroma component.

As a result, let us assume that 28×8 bits are used for compression onthe Cb plane component and 30×8 bits are used for compression on the Cbplane component. That is, in the present embodiment, the chromacomponent used bit ((28+30)×8 bits) is smaller than the chroma componenttarget bit ((32+32)×8 bits).

The compression management module 218 calculates the luma componenttarget bit on the luma component, using the chroma component used bit ofthe compressed data on the chroma component.

The compression management module 218 may calculate the luma componenttarget bit as follows.Luma component target bit=total target bit−chroma component usedbit=192×8 bits−(28+30)×8 bits=132×8 bits

Here, the total target bit is a value obtained by multiplying the sizeof total (16+8)×16×0.5=192 by the color depth value 8, in the case ofthe Y plane (520Y) of 16×16 size, the Cb plane (520Cb) of 8×8 size, andthe Cr plane (520Cr) of 8×8 size. Further, 0.5 means the targetcompression ratio.

The compression management module 218 allocates the luma componenttarget bit thus calculated to compress the luma component.

According to this embodiment, unlike the compressed bit stream 512including the Y component bit stream 512Y of 128 bits, the Cb componentbit stream 512Cb of 32 bits, and Cr component bit stream 512Cr of 32bits of FIG. 9, the compressed bit stream 522 including the Cb componentbit stream 522Cb of 28 bits, the Cr component bit stream 522Cr of 30bits and the Y component bit stream 522Y of 134 bits becomes thecompression result.

As described above, the frame buffer compressor 200 may generate acompressed bit stream 522, by merging the compressed data of the firstcomponent and the compressed data of the second component in anarbitrary sequence difference from the compression sequence of the firstcomponent (e.g., luma component) and the second component (e.g., chromacomponent). That is, the sequence of the Y component bit stream 522Y,the Cb component bit stream 522Cb, and the Cr component bit stream 522Crin the compressed bit stream 522 may be different from that illustratedin FIG. 10.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 interleaves and merges the compressed data of thefirst component and the compressed data of the second component togenerate a compressed bit stream 522. That is, in the compressed bitstream 522, the Y component bit stream 522Y, the Cb component bit stream522Cb, and the Cr component bit stream 522Cr may be generated, forexample, in the form in which the bit streams of Y, Cb, and Crcomponents repeated in units of pixels of the image data 10 are mixed inan arbitrary sequence. In this way, within the same total target bit, byassigning more bits to luma components having a higher importance andrelatively lower compression efficiency, and by assigning fewer bits tothe relatively different chroma components, the compression quality ofthe compressed data 20 obtained by compressing the image data 10 can beimproved.

Next, referring to FIG. 11, the first component of the image data 10,that is, the luma component corresponds to the Y plane 530Y of the imagedata 10, and the second component of the image data 10, that is, thechroma component corresponds to the Cb plane 530 Cb and the Cr plane530Cr of the image data 10.

In this embodiment, the compression management module 218 controls thecompression sequence so that the frame buffer compressor 200 compressesthe chroma component first and then compresses the luma component. Tothis end, the compression management module 218 calculates the chromacomponent target bit, before calculating the luma component target bit.However, the difference from the embodiment of FIG. 10 is that thecompression management module 218 can previously set the compressionratio for the chroma component to, for example, 40.625% smaller than50%.

Accordingly, in the case of the Cb plane 530Cb and the Cr plane 530Cr,the Cb plane component target bit and the Cr plane component target bitcan be calculated as follows.Cb plane component target bit=8×8×8×0.40625 bit=26×8 bitsCr plane component target bit=8×8×8×0.40625 bit=26×8 bits

The compression management module 218 first performs compression on thechroma component in accordance with the compression ratio set in advanceto, for example, 40.625%. Specifically, the compression managementmodule 218 determines the QP value and the entropy k value to conform tothe preset compression rate, and performs compression on the chromacomponent. As a result, 26×8 bits are used for compression of the Cbplane component and 26×8 bits are used for compression of the Cb planecomponent.

The compression management module 218 may calculate the luma componenttarget bit as follows.Luma component target bit=total target bit−chroma component target bitaccording to preset compression ratio=192×8 bits−(26+26)×8 bits=140×8bits

Here, the total target bit is a value obtained by multiplying the sizeof total (16+8)×16×0.5=192 by the color depth value 8, in the case ofthe Y plane (530Y) of 16×16 size, the Cb plane (530Cb) of 8×8 size, andthe Cr plane (530Cr) of 8×8 size. Further, 0.5 means the targetcompression ratio.

The compression management module 218 allocates the luma componenttarget bit thus calculated to compress the luma component.

Thus, in at least one embodiment of the present inventive concept, whenthe image data 10 conforms to the YUV 420 format, the chroma componenttarget bit may be calculated to the total target bit/3 XW by thecompression management module 218 (here, W is a positive real numberequal to or less than 1). For example, the embodiment of FIG. 11illustrates a case where the value of W is 0.40625.

According to this embodiment, unlike the compressed bit stream 512including the Y component bit stream 512Y of 128 bits, the Cb componentbit stream 512Cb of 32 bits, and the Cr component bit stream 512Cr of 32bits of FIG. 9, the compressed bit stream 532 including the bit Cbcomponent bit stream 532Cb of 26 bits, the Cr component bit stream 532Crof 26 bits, and the Y component bit stream 522Y of 140 bits becomes thecompression result.

As described above, the frame buffer compressor 200 may generate thecompressed bit stream 532, by merging the compressed data of the firstcomponent and the compressed data of the second component, in anarbitrary sequence different from the compression sequence of the firstcomponent (e.g., luma component) and the second component (e.g., chromacomponent). That is, the sequence of the Y component bit stream 532Y,the Cb component bit stream 532Cb and the Cr component bit stream 532Crin the compressed bit stream 532 may be different from that illustratedin FIG. 11.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 generates the compressed bit stream 532, byinterleaving and merging the compressed data of the first component andthe compressed data of the second component. That is, the Y componentbit stream 532Y, the Cb component bit stream 532Cb, and the Cr componentbit stream 532Cr may be generated within the compressed bit stream 532,for example, in the form in which the bit streams of Y, Cb, and Crcomponents repeated in units of pixels of the image data 10 are mixed inan arbitrary sequence.

As described above, within the same total target bit, by assigning morebits to the luma components with higher importance to have a relativelylower compression efficiency, and by assigning fewer bits of therelatively different chroma components, the compression quality of thecompressed data 20 obtained by compressing the image data 10 may beimproved.

FIGS. 12 to 14 are schematic views for explaining the operation of theimage processing device for the YUV 422 format data according to anexemplary embodiment of the present inventive concept.

FIGS. 12 and 13 illustrate a case where the target compression ratio ofthe image data 10 is 50% and the color depth is 8 bits when the imagedata 10 conforms to the YUV 420 format.

Referring to FIG. 12, the first component of the image data 10, that is,the luma component corresponds to the Y plane 540Y of the image data 10,and the second component of the image data 10, that is, the chromacomponent corresponds to the Cb plane 540Cb and the Cr plane 540 Cr ofthe image data 10.

In the case of the Y plane 540Y, since the target compression ratio is50% and the color depth is 8 bits, the luma component target bit may becalculated as follows.Luma component target bit=16×16×8×0.5 bit=128×8 bits

In the case of the Cb plane 540Cb and the Cr plane 540Cr, the Cb planecomponent target bit and the Cr plane component target bit may becalculated as follows.Cb plane component target bit=16×8×8×0.5 bit=64×8 bitsCr plane component target bit=16×8×8×0.5 bit=64×8 bits

As a result, the chroma component target bit obtained by adding the Cbplane component target bit and the Cr plane component target bit is128×8 bits.

When the luma component and the chroma component are compressed on thebasis of the target bit calculated in this manner, both the lumacomponent and the chroma component are compressed at the samecompression ratio of 50%.

The compressed bit stream 542 corresponding to the compression resultmay be formed as a single bit stream having a sequence of, for example,a Y component bit stream 542Y, a Cb component bit stream 542Cb, and a Crcomponent bit stream 542Cr. However, the scope of the present inventiveconcept is not limited thereto. For example, the frame buffer compressor200 may generate the compressed bit stream 542, by merging thecompressed data of the first component and the compressed data of thesecond component in an arbitrary sequence different from the compressionsequence of the first component (e.g., luma component) and the secondcomponent (e.g., chroma component). That is, the sequence of the Ycomponent bit stream 542Y, the Cb component bit stream 542Cb and the Crcomponent bit stream 542Cr in the compressed bit stream 542 may bedifferent from that illustrated in FIG. 12.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 generates the compressed bit stream 542, byinterleaving and merging the compressed data of the first component andthe compressed data of the second component. That is, the Y componentbit stream 542Y, the Cb component bit stream 542Cb, and the Cr componentbit stream 542Cr may be generated in the compressed bit stream 542, forexample, in the form in which the bit streams of the Y, Cb, and Crcomponents repeated in units of pixels of the image data 10 are mixed inan arbitrary sequence.

For example, the compressed bit stream 542 may be interleaved and mergedin the sequence in which a Y component bit stream of the first pixel ofthe image data 10, a Cb component bit stream of the first pixel, a Crcomponent bit stream of the first pixel, the Y component bit stream ofthe second pixel of the image data 10, the Cb component bit stream ofthe second pixel, and the Cr component bit stream of the second pixelare connected, and the interleaving sequence of Y, Cb, and Cr componentsmay also be determined in an arbitrary sequence.

Referring to FIG. 13, the first component of the image data 10, that is,the luma component corresponds to the Y plane 550Y of the image data 10,and the second component of the image data 10, that is, the chromacomponent corresponds to the Cb plane 550Cb and the Cr plane 550Cr ofthe image data 10.

In this embodiment, the compression management module 218 controls thecompression sequence so that the frame buffer compressor 200 compressesthe chroma component first and then compresses the luma component. Tothis end, the compression management module 218 first calculates thechroma component target bit, before calculating the luma componenttarget bit.

In the case of the Cb plane 520Cb and the Cr plane 520Cr, the Cb planecomponent target bit and the Cr plane component target bit may becalculated as follows.Cb plane component target bit=16×8×8×0.5 bit=64×8 bitsCr plane component target bit=16×8×8×0.5 bit=64×8 bits

The compression management module 218 allocates the chroma componenttarget bit to first perform the compression on the chroma component,before calculating the luma component target bit. Specifically, thecompression management module 218 determines the QP value and theentropy k so that the chroma component used bit becomes a value smallerthan and closest to the chroma target bit, and performs the compressionon the chroma component.

As a result, let us assume that 62×8 bits are used for compression ofthe Cb plane component and 60×8 bits are used for compression of the Cbplane component. That is, in the present embodiment, the chromacomponent used bit ((62+60)×8 bits) is smaller than the chroma componenttarget bit ((64+64)×8 bits).

The compression management module 218 calculates the luma componenttarget bit of the luma component, using the chrominance component usedbit of the compressed data on the chroma component.

Now, the compression management module 218 may calculate the lumacomponent target bit as follows.Luma component target bit=total target bit−chroma component usedbit=256×8 bits−(62+60)×8 bits=134×8 bits.

Here, the total target bit is a value obtained by multiplying the totalsizes (16+8+8)×16×0.5=256 by the color depth value 8, in the case of theY plane 550Y of 16×16 size, the Cb plane 550Cb of 8×8 size and the Crplane 550Cr of 8×8 size. Further, 0.5 means the target compressionratio.

The compression management module 218 allocates the luma componenttarget bit thus calculated to compress the luma component.

According to the present embodiment, unlike the compressed bit stream542 including the Y component bit stream 542Y of 128 bits, the Cbcomponent bit stream 542Cb of 64 bits and the Cr component bit stream542Cr of 64 bits of FIG. 12, the compressed bit stream 552 including theCb component bit stream 552Cb of 62 bits, the Cr component bit stream552Cr of 60 bits and the Y component bit stream 552Y of 134 bits becomesthe compression result.

As described above, the frame buffer compressor 200 may generate thecompressed bit stream 552, by merging the compressed data of the firstcomponent and the compressed data of the second component, in anarbitrary sequence different from the compression sequence of the firstcomponent (e.g., luma component) and the second component (i.e., chromacomponent). That is, the sequence of the Y component bit stream 552Y,the Cb component bit stream 552Cb and the Cr component bit stream 552Crin the compressed bit stream 552 may be different from that illustratedin FIG. 13.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 generates a compressed bit stream 552, byinterleaving and merging the compressed data of the first component andthe compressed data of the second component. That is, the Y componentbit stream 552Y, the Cb component bit stream 552Cb, and the Cr componentbit stream 552Cr in the compressed bit stream 552 may be generated, forexample, in the form in which the bit streams of Y, Cb, and Crcomponents repeated in units of pixels of the image data 10 are mixed inan arbitrary sequence.

In this way, within the same total target bit, by assigning more bits toluma components with higher importance and relatively lower compressionefficiency, and by assigning fewer bits to the relatively differentchroma components, the compression quality of the compressed data 20obtained by compressing the image data 10 may be improved.

Next, referring to FIG. 14, the first component of the image data 10,that is, the luma component corresponds to the Y plane 560Y of the imagedata 10, and the second component of the image data 10, that is, thechroma component corresponds to the Cb plane 560Cb and the Cr plane560Cr of the image data 10.

In the present embodiment, the compression management module 218controls the compression sequence so that the frame buffer compressor200 first compresses the chroma component and then compresses the lumacomponent. To this end, the compression management module 218 firstcalculates the chroma component target bit, before calculating the lumacomponent target bit. However, the difference from the embodiment ofFIG. 13 is that the compression management module 218 previously set thecompression ratio for the chroma component to, for example, 40.625%smaller than 50%.

Accordingly, in the case of the Cb plane 560Cb and the Cr plane 560Cr,the Cb plane component target bit and the Cr plane component target bitmay be calculated as follows.Cb plane component target bit=16×8×8×0.40625 bit=52×8 bitsCr plane component target bit=16×8×8×0.40625 bit=52×8 bits

The compression management module 218 first performs compression on thechroma component first, in accordance with the compression ratiopreviously set to, for example 40.625%. Specifically, the compressionmanagement module 218 determines the QP value and the entropy k value toconform to the preset compression rate, and performs compression on thechroma component. As a result, 52×8 bits were used for compression ofthe Cb plane component, and 52×8 bits were used for compression of theCb plane component.

Now, the compression management module 218 may calculate the lumacomponent target bit as follows.Luma component target bit=total target bit−chroma component target bitaccording to preset compression ratio=256×8 bits−(52+52)×8 bits=152×8bits

Here, the total target bits is a value obtained by multiplying the totalsize (16+8+8)×8=256 by the color depth value 8, in the case of the Yplane 560Y of 16×16 size, the Cb plane 560Cb of 8×8 size and the Crplane 560Cr of 8×8 size. Further, 0.5 means the target compressionratio.

The compression management module 218 allocates the luma componenttarget bit thus calculated and compresses the luma component.

Thus, in at least one embodiment of the present inventive concept, whenthe image data 10 conforms to the YUV 422 format, the chroma componenttarget bit may be calculated to the total target bit/2 XW by thecompression management module 218 (here, W is a positive real numberequal to or less than 1). For example, the embodiment of FIG. 14illustrates a case where the value of W is 0.5.

According to the present embodiment, unlike the compressed bit stream542 including the Y component bit stream 542Y of 128 bits, the Cbcomponent bit stream 542Cb of 64 bits, and the Cr component bit stream562 of 64 bits of FIG. 12, the compressed bit stream 562 including theCb component bit stream 542Cb of 52 bits, the Cr component bit stream562Cr of 52 bits, and the Y component bit stream 562Y of 152 bitsbecomes the compression result.

As described above, the frame buffer compressor 200 may generate thecompressed bit stream 562, by merging the compressed data of the firstcomponent and the compressed data of the second component in anarbitrary sequence different from the compression sequence of the firstcomponent (e.g., luma component) and the second component (i.e., chromacomponent). That is, the sequence of the Y component bit stream 562Y,the Cb component bit stream 562Cb and the Cr component bit stream 562Crin the compressed bit stream 532 may be different from that illustratedin FIG. 14.

In an exemplary embodiment of the present inventive concept, the framebuffer compressor 200 generates the compressed bit stream 562, byinterleaving and merging the compressed data of the first component andthe compressed data of the second component. That is, in the compressedbit stream 532, the Y component bit stream 562Y, the Cb component bitstream 562Cb, and the Cr component bit stream 562Cr may be generated inthe form in which the bit streams of Y, Cb, and Cr components repeatedin units of pixels of the image data 10 are mixed in an arbitrarysequence.

In this way, within the same total target bit, by assigning more bits toluma components with higher importance and relatively lower compressionefficiency, and by assigning fewer bits to the relatively differentchroma components, the compression quality of the compressed data 20obtained by compressing the image data 10 can be improved.

FIG. 15 is a flowchart illustrating a method for operating the imageprocessing device according to an exemplary embodiment of the presentinventive concept.

Referring to FIG. 15, the method for operating an image processingdevice according to an exemplary embodiment of the present inventiveconcept includes calculating a target bit for the chroma component(S1501).

Specifically, before calculating the target bit for the chromacomponent, the image processing device calculates the total target biton the basis of the target compression ratio of the image data 10conforming to the YUV format, and then calculates the chroma componenttarget bit for compressing the chroma component including the Cb and Crcomponents in the YUV format.

Further, the method includes assigning the chroma component target bitto compress the chroma component (S1503).

In addition, the method includes obtaining a number of compressed bitsfor the chroma component (S1505). The number of compressed bits for thechroma component may be referred to as chroma component used bit of thecompressed data for the chroma component.

The method further includes calculating target bits for the lumacomponent (e.g., the target bit of the luma component) (S1507). The lumacomponent is the Y component in the YUV format.

Further, the method includes assigning the luma component target bit tocompress the luma component (S1509).

Further, the method may further include adding a dummy bit after thecompressed data of the luma component, when the sum of the lumacomponent used bit of the compressed data of the luma component and thechroma component used bit is less than the total target bit.

Those skilled in the art will appreciate that many variations andmodifications can be made to the exemplary embodiments withoutsubstantially departing from the principles of the present inventiveconcept.

What is claimed is:
 1. An image processing device comprising: amultimedia intellectual property (IP) block configured to process imagedata including a first component comprising a luma component and asecond component comprising a chroma component; a memory; and a framebuffer compressor (FBC) configured to compress the image data togenerate compressed data and store the compressed data in the memory,wherein the frame buffer compressor includes a logic circuit configuredto control a compression sequence of the first component and the secondcomponent of the image data, wherein the logic circuit calculates achroma component target bit from the chroma component and a targetcompression ratio of the image data, calculates a first luma componenttarget bit from the luma component and the target compression ratio,assigns at least one bit of the chroma component target bit to the firstluma component target bit to generate a second luma component targetbit, compresses the chroma component according to the remaining bits ofthe chroma component target bit and compresses the luma componentaccording to the second luma component target bit.
 2. The imageprocessing device of claim 1, wherein after compressing the firstcomponent and the second component in accordance with the compressionsequence determined by the logic circuit, the frame buffer compressormerges the compressed data of the first component and the compresseddata of the second compressed data to generate a single bit stream. 3.The image processing device of claim 2, wherein the frame buffercompressor merges the compressed data of the first component and thecompressed data of the second component in an arbitrary sequencedifferent from the compression sequence of the first component and thesecond component to generate the single bit stream.
 4. The imageprocessing device of claim 2, wherein the frame buffer compressorinterleaves and merges the compressed data of the first component andthe compressed data of the second component to generate the single bitstream.
 5. The image processing device of claim 1, wherein the imagedata is image data conforming to a YUV format, the luma componentincluding a Y component in the YUV format, and the chroma componentincluding Cb and Cr components in the YUV format.
 6. The imageprocessing device of claim 1, wherein the logic circuit controls thecompression sequence so that the frame buffer compressor firstcompresses the chroma component first and then compresses the lumacomponent.
 7. The image processing device of claim 1, wherein the chromacomponent used bit is smaller than the chroma component target bit. 8.The image processing device of claim 1, wherein, when the image dataconforms to the YUV 420 format, the chroma component target bit is setto a total target bit/3×W, where W is a positive real number <=1, wherethe total target bit is determined from the image data and the targetcompression ratio.
 9. The image processing device of claim 1, wherein,when the image data conforms to the YUV 422 format, the chroma componenttarget bit is set to a total target bit/2×W, where W is a positive realnumber <=1, where the total target bit is determined from the image dataand the target compression ratio.
 10. The image processing device ofclaim 1, wherein the second luma component target bit is calculated byadding a count of the assigned at least one bit to the first lumacomponent target bit.
 11. An image processing device comprising: amultimedia intellectual property (IP) block configured to process imagedata conforming to a YUV format including a chroma component and a lumacomponent, the chroma component including Cb and Cr components, the lumacomponent including a Y component; a memory; and a frame buffercompressor (FBC) configured to compress the image data to generatecompressed data and store the compressed data in the memory, wherein theframe buffer compressor includes a logic circuit configured to control acompression sequence such that a first compression operation having afirst compression ratio applied to the chroma component is executedprior to a second compression operation having a second compressionratio applied to the luma component, wherein the second compressionratio is decreased prior to executing the second compression operationwhen a result of the first compression operation exceeds the firstcompression ratio.
 12. The image processing device of claim 11, whereinthe logic circuit calculates a total target bit and a chroma componenttarget bit of the chroma component based on a target compression ratioof the image data, assigns the chroma component target bit to compressthe chroma component, calculates a luma component target bit of the lumacomponent, using a chroma component used bit of the compressed data forthe chroma component, and assigns the luma component target bit tocompress the luma component.
 13. The image processing device of claim12, wherein, when the image data conforms to the YUV 420 format, thechroma component target bit is set to the total target bit/3×W, where Wis a positive real number >=1.
 14. The image processing device of claim12, wherein, when the image data conforms to the YUV 422 format, thechroma component target bit is set to the total target bit/2×W, where Wis a positive real number <=1.
 15. The image processing device of claim12, wherein the luma component target bit is calculated by subtractingthe chroma component used bit from the total target bit.
 16. The imageprocessing device of claim 12, wherein, when a sum of the luma componentused bit of the compressed data of the luma component and the chromacomponent used bit is less than the total target bit, the compressionmanagement module adds a dummy bit after the compressed data of the lumacomponent.
 17. The image processing device of claim 12, wherein thechroma component used bit is smaller than the chroma component targetbit.
 18. The image processing device of claim 17, wherein the logiccircuit determines a quantization parameter (QP) value and an entropy kencoding value so that the chroma component used bit is a value smallerthan and closest to the chroma target bit.
 19. A method for operating animage processing device, the method comprising: calculating a totaltarget bit based on a target compression ratio of image data conformingto a YUV format; calculating a chroma component target bit forcompressing a chroma component including Cb and Cr components of the YUVformat; assigning the chroma component target bit to compress the chromacomponent; calculating the luma component target bit of the lumacomponent including a Y component of the YUV format, using the chromacomponent used bit of the compressed data for the chroma component;assigning the luma component target bit to compress the luma component;and adding a dummy bit after the compressed data of the luma component,when the sum of the luma component used bit of the compressed data ofthe luma component and the chroma component used bit is less than thetotal target bit.